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    <title>fr.lig.sigma.operators package</title>
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Base of all operators implementation considering the definitions of AStrAL. As a reminder, the operator definitions can
be found <a href="http://loic.doesntexist.com/mediawiki/index.php/Main_Page">here</a>.

This package gives the minimum framework to write quickly any type of operators. With the abstract classes like
{@link fr.lig.sigma.astral.operators.RelationOperator} or {@link fr.lig.sigma.astral.operators.StreamOperator},
implementing an operator can be nearly reduced to it's core algorithm.

<h3>Common rules to define an operator</h3>
Each operator, are classes that implements the interface {@link fr.lig.sigma.astral.operators.Operator} as well as their
right output entity type. An interface must be defined for that, like {@link fr.lig.sigma.astral.operators.pi.Pi} for
example with an unique function that will initialize the operator with its input and parameters.

The implementation must follow very simple rules to define a good operators.
<ul>
    <li>Extends on of the two abstract operators that extends {@link fr.lig.sigma.astral.common.structure.EntityContainer}</li>
    <li>Do a setOutput as soon as enough details about the attributes and names are gathered</li>
    <li>Then only, do a addInput to indicate to the scheduler the dependencies of the operator, and if it is the case,
    to be registered as an input listener.</li>
    <li>Implement your algorithm inside the processEvent of {@link fr.lig.sigma.astral.common.event.EventProcessor}</li>
</ul>

If your operator is a composite and needs to create other operators, just extends the interface with
{@link fr.lig.sigma.astral.operators.OperatorFactory}. The core will detect it at the instanciation and will attach the
right one to this component.
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